Kawasaki Ki.64 ("Rob")

The Kawasaki Ki-64 to meet a 1940 specification for a fighter capable of
435 mph and reaching 16,400 feet in five minutes. The resulting design was
interesting in that it used the Kawasaki Ha-201 engine, which was actually
two Ha-40 12-cylinder engines mounted in tandem fore and aft of the pilot's
cockpit, which drove two contra-rotating propellers. Another unique feature
of the Ki-64 was the steam vapor cooling system for the engines, which was
installed in the wings. First flights occurred in December of 1943. A
production version with a more powerful engine was believed to be capable of
497 mph, but the project was canceled in favor of more conventional aircraft
already in production.